Cosmetic emulsions containing copolymers of alkyl(meth)acrylates and mono-(N-hydroxyalkyl) or bis-(N-hydroxyalkyl) (meth)acrylamides

ABSTRACT

Water-in-oil emulsions containing from 2% to 20% by weight of polymeric emulsifiers comprising statistical copolymers composed of units of the general formulae ##STR1## in the molar ratio of (I) to (II) of 2:1 to 20:1, wherein X is hydrogen or methyl, R 1  is alkyl having 6 to 24 carbon atoms, and R 2  is --NH--CH 2  OH, --NH--CH 2  CH 2  OH, or --N(CH 2  CH 2  OH) 2  ; 20 to 75% by weight of water; and the remainder to 100% by weight of conventional oily substances used in cosmetic emulsions.

FIELD OF THE INVENTION

The invention relates to cosmetic emulsions of the water-in-oil typehaving a content of copolymers of alkyl(meth)acrylates andmono-(N-hydroxyalkyl) or bis-(N-hydroxyalkyl) (meth)acrylamides asemulsifiers. The invention includes the emulsions themselves and methodsfor the preparation thereof.

RELATED ART

In contrast to the production of oil-in-water emulsions, only a limitednumber of emulsifying agents are available for producing cosmeticemulsions of the water-in-oil type and, moreover, the best of theseemulsifying agents are becoming increasingly scarce. Even nowadays, woolfat and its derivatives are still some of the most important bases foremulsifying agents for producing creams of the water-in-oil type.However, despite their uncontested advantages, both wool fat and itsderivatives, such as lanolin, have certain disadvantages. Thusconventional water-in-oil emulsifying agents based on wool fat and itsderivatives impart a strong characteristic odor to the creams preparedwith these substances. This, in turn, requires strong perfuming whichfrequently cannot be tolerated by persons having sensitive skin.However, this influencing of the quality of the cream by a strongcharacteristic odor is not only peculiar to wool fat and itsderivatives, but also extends to lanolin-free water-in-oil emulsifyingagents based on animal sterols, particularly such emulsifying agentsbased on cholesterol. Furthermore, low-molecular weight emulsifyingagents, together with the effective substances of the cream, can beabsorbed by the skin, which is not desirable in all cases.

In addition to the said emulsifying agents based on wool fat, waxalcohols and sterols, the most widely known water-in-oil emulsifiers forcosmetic purposes include the oleic acid esters for various polyols,such as glycerin, pentaerythritol, trimethylolpropane and sorbitol.However, due to the unsaturation in their acid component the oleic acidesters have various disadvantages with respect to their technical use,so that there is a genuine need for new and suitable water-in-oilemulsifying agents.

OBJECTS OF THE INVENTION

One object of the present invention is the development of a cosmeticemulsion or cream of the water-in-oil type which can be prepared easilyand safely from inexpensive materials without need for costlyemulsifying equipment.

Another object of the invention is the development of a cosmeticemulsion of the above type which is substantially odorless and which,therefore, can find general acceptance when containing only a small andharmless amount of perfume.

A particular object of the invention is the production of a cosmeticemulsion of the above type comprising (1) from 2% to 20% by weight of apolymeric emulsifier capable of forming water-in-oil emulsions composedof units of the general formulae ##STR2## in the molar ratio of (I) to(II) of 2:1 to 20:1, wherein X is hydrogen or methyl, R₁ is alkyl having6 to 24 carbon atoms and R₂ is --NH--CH₂ OH, --NH--CH₂ CH₂ OH, or--N(CH₂ CH₂ OH)₂ ; (2) from 20 to 75% by weight of water; and (3) theremainder to 100% by weight of conventional oily substances used incosmetic emulsions.

These and other objects of the present invention will become moreapparent as the description thereof proceeds.

DESCRIPTION OF THE INVENTION

It has now been disovered that the objectionable features of the priorart emulsifiers have been overcome and the above objects have beenachieved by the discovery of cosmetic emulsions of the water-in-oil typecontaining (1) from 2% to 20% by weight, relative to the total weight ofthe emulsion, of statistical copolymers, which are composed, in themolar ratio of (I) to (II) of 2:1 to 20:1, more preferably 3:1 to 12:1,of units of the general formulae ##STR3## wherein X is hydrogen or amethyl radical, R₁ is an alkyl radical of 6 to 24 carbon atoms, and R₂is a radical selected from the group consisting of --NH--CH₂ OH,--NH--CH₂ CH₂ OH, and --N(CH₂ CH₂ OH)₂, (2) from 20% to 75% by weight ofwater, relative to the total weight of the emulsion, and (3) theremainder to 100% by weight of conventional oil substances used incosmetic emulsions, such as vegetable and animal fats, waxes, fattyalcohols, hydrocarbons, as well as other auxiliary substances normallyused in cosmetic emulsions.

The preparation of the copolymers of alkyl(meth) acrylates andmono-(N-hydroxyalkyl) or bis-(N-hydroxyalkyl) (meth)acrylamides used asemulsifiers in the cosmetic emulsions of the invention can be effectedin known manner in one step under the usual conditions of radicalpolymerization. The polymerization can be carried out with nonpolarsolvents, such as benzene or toluene, or in polar solvents, such asmethanol, methyl ethyl ketone or tetrahydrofuran, by means of peroxides,such as dibenzoyl peroxide or lauroyl peroxide, and azo compounds, suchas azobisisobutyronitrile as a catalyst.

The technical production is preferably effected in the form of asolution polymerization, in those solvents which dissolve only themonomers, but not the polymer (precipitation polymerization)particularly since this results in satisfactorily precipitable polymerswhich are practically free of monomers (J. Scheiber, Chemie undTechnologie der Kunstlichen Harze, Vol. I, pages 362 ff, 1961.

The monomeric starting compounds from which the polymer units (II) ofthe copolymers of the invention are derived are mono- orbis-(N-hydroxyalkyl) (meth) acrylamides which are in part commerciallyavailable products, such as N-hydroxymethyl acrylamide, or productswhich are known in the literature, such as N-hydroxymethylmethacrylamide, (C.A. 66, pg. 66, 705 c), N-2-hydroxyethyl acrylamide(C.A. 66, p. 29, 497 r), N-2hydroxyethyl methacrylamide (C.A. 64, p.1970, g), bis-(n-2-hydroxyethyl) acrylamide, (C.A. 66, p. 29, 497 r) andbis- N-2-hydroxyethyl)methacrylamide (C.A. 56, p. 1616,i). They areprepared by methods known in the art.

Examples of such monomeric starting compounds are N-hydroxymethylacrylamide, N-hydroxymethyl methacrylamide, N-2-hydroxyethyl acrylamide,and bis-(N-2-hydroxyethyl) methacrylamide. N-hydroxymethyl acrylamidehas been found to be a very useful monomer.

The monomeric starting compounds from which the polymer units (I) of thecopolymers of the invention are derived have the formula ##STR4##wherein X is hydrogen or methyl, and R₁ is an alkyl radical having 6 to24, more preferably 8 to 14, carbon atoms.

Among the monomeric starting compounds of the formula (III) above may bementioned hexyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, nonylacrylate, decyl acrylate, lauryl acrylate, myristyl acrylate, cetylacrylate stearyl acrylate, behenyl acrylate, hexyl methacrylate, octylmethacrylate, nonyl methacrylate, decyl methacrylate, laurylmethacrylate, myristyl methacrylate, cetyl methacrylate, stearylmethacrylate and behenyl methacrylate.

Among the preferred monomers of the formula (III) are the acrylic andmethacrylic acid esters of the fatty alcohols having 8 to 14 carbonatoms in the alkyl radical such as octyl acrylate, nonyl acrylate, decylacrylate, lauryl acrylate, myristyl acrylate, octyl methacrylate, nonylmethacrylate, decyl methacrylate, lauryl methacrylate, and myristylmethacrylate.

In the copolymers of the invention, the molar ratio of the mono- orbis-(N-hydroxyalkyl) (meth) acrylamide monomer: alkyl (meth) acrylatemonomer are from 1:2 to 1:20, preferably from 1:3 to 1:12.

The copolymers of the invention have average molecular weights between2,000 and 100,000. Those having average molecular weights between 3,000and 20,000 are particularly suitable in view of their easyprocessability and the quality of the emulsions obtained. Thesemolecular weights can be adjusted in a known manner by the amount ofcatalyst, the nature and amount of the solvent, and by the addition ofpolymerization regulators.

The emulsions in accordance with the invention are produced in a simpleand known manner by dissolving the copolymers, acting as the emulsifyingagents, in the oil phase at a temperature of approximately 60° to 70° C.Subsequently, the desired quantity of water, heated to approximately 60°C. to 65° C. is added, and the emulsion obtained is stirred whilecooling.

Cosmetically effective amounts of further constituents of the cosmeticemulsions being manufactured, such as skin moisture regulators,vegetable extracts of effective substances, vitamins, hormones,pigments, salts, perfume oils, UV filtering substances, dyestuffs, etc.,are advantageously dissolved or distributed in the phase which absorbsthese substances to best advantage. The quantity of emulsifying agentrequired is 2% to 20% by weight, preferably 5% to 10% by weight,relative to the total cosmetic emulsion. The amount of water to beincorporated can be 20% to 75% by weight, preferably 45% to 65% byweight, relative to the total cosmetic emulsion.

Products conventionally used, such as animal and vegetable oils andfats, synthetic esters or fatty acids with aliphatic alcohols, higherfatty alcohols, waxes, so-called mineral fats and oils, such as paraffinoil, "Vaseline"®, ceresine, silicone oils and silicone fats are suitableas the oil phase of the cosmetic emulsions in accordance with theinvention.

The invention thus also includes a composition which when agitated withwater forms a cosmetic emulsion of the water-in-oil type, comprising (1)from 2% to 20% by weight, relative to the total weight of saidcomposition, of a polymeric emulsifier which is a copolymer composed, inthe molar ratio of (I) to (II) of 2:1 to 20:1, of units of the generalformulae ##STR5## wherein X is hydrogen or a methyl radical, R₁ is analkyl radical of 6 to 24 carbon atoms, and R₂ is a radical selected fromthe group consisting of --NH--CH₂ OH, --NH--CH₂ CH₂ OH, and --N(CH₂ CH₂OH)₂, and (2) the remainder to 100% by weight of the composition ofconventional oily substances used in cosmetic emulsions. Suchconventional oily substances include animal and vegetable oils and fats,synthetic esters of fatty acids with aliphatic alcohols, higher fattyalcohols, waxes, so-called mineral fats and oils, such as paraffin oil,"Vaseline"®, ceresin, silicone oils and silicone fats. In addition thecosmetic emulsions or creams can contain, if desired, other auxiliarysubstances normally used in cosmetic emulsions. Examples of suchauxiliary substances are skin moisture regulators, vegetable extracts ofeffective substances, vitamins, hormones, pigments, salts, perfume oils,UV filtering substances, dyestuffs, etc.

German Offenlegungsschrift (DOS) No. 2,116,787 has already described theuse of water-in-oil emulsifying agents in the form of sequence polymerswhich at the same time have at least one lipophilic sequence and onehydrophilic sequence. Each sequence should have the properties of thecorresponding homopolymer. These sequence polymers are obtained byanionic polymerization, which places high demands on the purity of thesubstances used, and requires working at low temperatures underprotective gas and increased safety precautions when handlingspontaneously combustible catalysts. In contrast to this, theemulsifying agents required for producing the emulsions in accordancewith the present invention can be manufactured in a simple manner.

According to German Offenlegungsschrift (DOS) No. 1,745,216, copolymersof a monomer with a lipophilic chain and a monomer with a carboxylicacid anhydride function are suggested as emulsifiers for water-in-oilemulsions. But these products are sensitive to hydrolysis, and, to avoidthis disadvantage, a further processing step in addition to thepolymerization, is required in order to convert them into a more stableform.

In general, the emulsions in accordance with the present invention canalso be used by persons having a sensitive skin. Since they do not haveany appreciable characteristic odor, they do not require heavyperfuming, which in turn, has an advantageous effect upon thecompatibility and also reduces costs.

Furthermore, the emulsions according to the invention are characterizedby low sensitivity to acid, thus rendering it possible to incorporateacidic raw materials therein, such as organic acids. Another veryfavorable property of the emulsions according to the invention is theirhigh temperature stability, which enables them to withstand a thermalstress of 50° C. for 6 weeks without any detrimental effects.

In the specification and claims, the term "(meth) acrylate(s)" is usedto designate ester(s) of acrylic acid and ester(s) of methacrylic acid.Similarly, the term "(meth)acrylamide(s)" is used to designate amide(s)of acrylic acid and amide(s) of methacrylic acid.

The following examples further illustrate the invention, but withoutlimiting the invention to these examples.

EXAMPLES

The following example illustrates the preparation of a copolymer for usein the cosmetic emulsions of the present invention.

EXAMPLE 1 N-Hydroxymethyl acrylamide/dodecyl acrylate-copolymer (1:6molar ratio)

10.1 gm (0.1 mole) of N-hydroxymethyl acrylamide and 144 gm (0.6 mole)of dodecyl acrylate were dissolved in 360 gm of methyl ethyl ketone. Tothe solution obtained were added 3.1 gm of dibenzoyl peroxide as acatalyst. The reaction mixture was maintained for 5 hours under stirringat a temperature of 80° C. After the reaction was completed, the solventwas distilled off and the reaction product washed several times withmethanol. 147 gm (95% of theory) of N-hydroxymethyl acrylamide/dodecylacrylate copolymer (1:6 molar ratio) were obtained.

The other copolymers, used in the examples given below, were obtained inan analogous manner to the above method.

EXAMPLE 2

Cosmetic emulsions based on Vaseline®

A mixture of 10 gm of N-hydroxymethyl acrylamide/dodecyl acrylatecopolymer (1:6 molar ratio), and 40 gm of Vaseline® was melted togetherby heating to 65° C. To the melt was added 50 gm of water, which hadbeen heated to 65° C., and the mass was allowed to cool under constantstirring. The emulsion can be easily produced by manual stirring. Thecream is stable for several months and showed no change even after 6weeks at 50° C. By adding various conventional cosmetic agents andperfume oils, this basic cream can be used to produce various skincreams.

The following copolymers can also be used in the foregoing exampleinstead of N-hydroxymethyl acrylamide/dodecyl acrylate copolymer (1:6molar ratio) with equally good results.

    ______________________________________                                                                     Molar                                            Copolymer                    Ratio                                            ______________________________________                                        N-hydroxymethyl acrylamide/decyl acrylate                                                                  (1:3)                                            N-hydroxymethyl acrylamide/behenyl acrylate                                                                (1:2)                                            N-hydroxymethyl acrylamide/octyl acrylate                                                                  (1:12)                                           N-hydroxymethyl acrylamide/hexyl acrylate                                                                  (1:15)                                           N-hydroxymethyl acrylamide/cetyl acrylate                                                                  (1:8)                                            N-hydroxymethyl methacrylamide/decyl acrylate                                                              (1:10)                                           N-hydroxymethyl methacrylamide/octyl methacrylate                                                          (1:8)                                            N-2-hydroxyethyl acrylamide/dodecyl methacrylate                                                           (1:6)                                            N-2-hydroxyethyl acrylamide/myristyl acrylate                                                              (1:4)                                            N-2-hydroxyethyl methacrylamide/stearyl acrylate                                                           (1:2)                                            N-2-hydroxyethyl methacrylamide/decyl methacrylate                                                         (1:8)                                            bis-(N-2-hydroxyethyl)acrylamide/hexyl acrylate                                                            (1:20)                                           bis-(N-2-hydroxyethyl)acrylamide/octyl acrylate                                                            (1:12)                                           bis-(N-2-hydroxyethyl)acrylamide/dodecyl methacrylate                                                      (1:8)                                            bis-(N-2-hydroxyethyl)methacrylamide/myristyl                                                              (1:6)                                            acrylate                                                                      bis-(N-2-hydroxyethyl)methacrylamide/nonyl methacrylate                                                    (1:10)                                           ______________________________________                                    

EXAMPLE 3

Cosmetic emulsion based on peanut oil/decyl oleate mixture

A mixture of 4 gm of N-hydroxymethyl acrylamide/dodecyl acrylatecopolymer (1:6 molar ratio), 40 gm of a hardened peanut oil/decyl oleatemixture (90:10 by weight), 3 gm of beeswax, and 3 gm of glycerylmonooleate was melted together by heating to 70° C. To the melt wereadded under constant stirring 50 gm of water, which had been heated to65° C., and the paste was allowed to cool under constant stirring. Acream was obtained which was very similar in its stability properties tothe cream obtained in Example 2. By incorporating additionalcosmetically effective amounts of conventional cosmetically effectivesubstances, such as moisture regulators, vegetable extracts, and perfumeoils, various skin creams can be prepared from this basic cream.

The following copolymers can be used instead of N-hydroxymethylacrylamide/dodecyl acrylate copolymer (1:6 molar ratio) with equallygood results.

    ______________________________________                                                                    Molar                                             Copolymer                   Ratio                                             ______________________________________                                        N-hydroxymethyl acrylamide/cetyl acrylate                                                                 (1:4)                                             N-2-hydroxyethyl acrylamide/dodecyl acrylate                                                              (1:8)                                             N-2-hudroxyethyl acrylamide/octyl methacrylate                                                            (1:10)                                            N-hydroxymethyl acrylamide/stearyl acrylate                                                               (1:3)                                             N-2-hydroxyethyl methacrylamide/octyl acrylate                                                            (1:8)                                             /myristyl acrylate          (1:6)                                             bis-(N-2-hydroxyethyl)acrylamide/octyl methacrylate                                                       (1:12)                                            bis-(N-2-hydroxyethyl)acrylamide/dodecyl acrylate                                                         (1:8)                                             bis-(N-2-hydroxyethyl)methacrylamide/decyl acrylate                                                       (1:10)                                            bis-(N-2-hydroxyethyl)methacrylamide/decyl acrylate                                                       (1:4)                                             ______________________________________                                    

EXAMPLE 4

Cosmetic emulsions based on Vaseline®/decyl oleate mixture

A mixture of 7 gm of N-hydroxymethyl acrylamide/dodecyl acrylatecopolymer (1:6 molar ratio), 10 gm Vaseline®, 15 gm of decyl oleate, 3gm of beeswax, and 2 gm of calcium stearate was melted together byheating to 65° C. Into this mixture were stirred 63 gm of water, heatedto 65° C., and the stirring was continued until the emulsion becamecold. A cream was obtained which resembled the other two creamsdescribed above in its stability properties. By incorporatingconventional cosmetically effective substances and perfume oils, a largenumber of cosmetic creams can be produced based on this basic cream.

The N-hydroxymethyl acrylamide/dodecyl acrylate copolymer (1:6 molarratio), used as an emulsifier, can be replaced with equally good resultsby the same amount of N-2-hydroxyethyl acrylamide/octyl methacrylatecopolymer (1:10 molar ratio), bis-(N-2-hydroxyethyl)acrylamide/octylacrylate copolymer (1:12 molar ratio) and the other copolymers mentionedabove.

EXAMPLE 5

Cosmetic emulsion based on hardened peanut oil

A mixture of 6 gm of N-hydroxymethyl acrylamide/dodecyl acrylatecopolymer (1:6 molar ratio) and 44 gm of hardened peanut oil was meltedtogether by heating to 65° C. Into this mixture were stirred 50 gm ofwater, which had been heated to 65° C. After stirring until the emulsionwas cold, a cream was obtained which resembled to a great extent thepreviously mentioned creams in its stability properties. The cream canbe used as a basic cream for various cosmetic preparations, such asdescribed above.

Replacement of this example of the N-hydroxymethyl acrylamide/dodecylacrylate copolymer (1:6 molar ratio) by the other copolymers mentionedis readily possible.

We claim:
 1. A cosmetic emulsion of the water-in-oil type, comprising(1) from 2% to 20% by weight of statistical copolymers which arecomposed, in the molar ratio of (I) to (II) of 2:1 to 20:1, of units ofthe general formulae ##STR6## wherein X is hydrogen or a methyl radical,R₁ is an alkyl radical of 6 to 24 carbon atoms, and R₂ is a radicalselected from the group consisting of --NH--CH₂ OH, --NH--CH₂ CH₂ OH,and --N(CH₂ CH₂ OH)₂, (2) from 20% to 75% by weight of water, and (3)the remainder to 100% by weight of conventional oily substances used incosmetic emulsions.
 2. The cosmetic emulsion of claim 1 wherein R₁ is analkyl radical of 8 to 14 carbon atoms.
 3. The cosmetic emulsion of claim1 wherein the polymeric emulsifier has an average molecular weight offrom 2,000 to 100,000.
 4. The cosmetic emulsion of claim 3 wherein theaverage molecular weight is from 3,000 to 20,000.
 5. The cosmeticemulsion of claim 1 wherein the polymeric emulsifier is present in anamount from 5% to 10% by weight, relative to the total cosmeticemulsion.
 6. The cosmetic emulsion of claim 5 wherein the water ispresent in an amount of from 45% to 65% by weight, relative to the totalcosmetic emulsion.
 7. The cosmetic emulsion of claim 1 wherein, inaddition to the polymeric emulsifier and water, there are presentvegetable or animal fats, waxes, fatty alcohols and hydrocarbons as saidoily substances.
 8. In the method of producing a cosmetic emulsion ofthe water-in-oil type comprising mixing an emulsifier capable of formingwater-in-oil creams with a cosmetically acceptable oily material atelevated temperatures, mixing therewith from 20% to 75% by weight ofwater, cooling under agitation and recovering said cosmetic emulsion ofthe water-in-oil type, the improvement consisting of adding (1) from 2%to 20% by weight of the statistical copolymer of claim 1, (2) from 20%to 75% by weight of water and (3) the remainder to 100% by weight ofconventional oily substances used in cosmetic emulsions.
 9. Acomposition which when agitated with water forms a cosmetic emulsion ofthe water-in-oil type, comprising (1) from 2% to 20% by weight of thestatistical copolymer of claim 1, and (2) the remainder to 100% byweight of the composition of conventional oily substances used incosmetic emulsions.
 10. The cosmetic emulsion of claim 1 wherein themolar ratio of (I) to (II) is 3:1 to 12:1.